1. Field of the Invention
This invention relates to a bearing supporting system suitable for cone and gyratory crushers and especially for the so-called spiderless crushers which are designed to support a main shaft assembly with a mantle in a radial direction only at the lower side thereof without requiring bearing support to the upper side thereof. More particularly, the invention concerns a bearing supporting system which has a thrust bearing mounted in an improved manner for supporting a main shaft in the thrust direction, forming a suitable oil film on the bearing surface and ensuring a prolonged lifetime of a crusher.
2. Description of the Prior Art
In general, the crusher is provided with a mantle substantially of a truncated cone shape which is rotatable in an eccentric state within a concave ring substantially in the form of a conical cylinder to crush rocks of feed material by compression between the concave ring and mantle. The main shaft assembly with a mantle is supported by either a double supporting system which is adapted to support the upper and lower sides of the main shaft or by a single supporting system which is adapted to support only a lower side of a mantle shaft in a radial direction, leaving the upper side of the mantle shaft in a free state. The type which supports the upper and lower sides of a mantle shaft can provide a stable support of a simple construction but it requires mounting of radial support arms extending from the upper portion of the main shaft toward a concave ring. These radial support arms are located across a passage of feed material to be fed into the crusher, so that they form obstacles hindering the feed material from being fed freely in all directions. That is to say, the feeding becomes irregular in the circumferential direction, giving rise to a problem of uneven wear of the concave ring and mantle.
In contrast, in the latter case, it is possible to preclude the problem of uneven wear as mentioned above, and to feed material in an extremely smooth manner without creating any obstacle to feeding. However, owing to the cantilever-like support of a main shaft, a large load is imposed on the bearing, so that the bearing support system has to be constructed to endure operations under the conditions of heavy load.
An example of the cone crusher which is constructed to this effect is proposed in the conventional cone crusher in FIG. 1 and in Japanese patent publication No. 57-58216 as illustrated in FIG. 1A. The cone crusher shown in the figures is provided with a casing 1 consisting of an upper casing 3 and a lower casing 2, a concave ring 4 substantially in the form of a conical cylinder which is fitted on the inner surface of the upper casing 3, and a mantle 5 which is rotatably supported in the concave ring 4. The lower casing 2 is integrally provided with a support cylinder 6 at the bottom thereof, the support cylinder 6 having an eccentric drive shaft 8 substantially in the form of a conical cylinder rotatably fitted thereon through a radial bearing 7 fitted on the inner surface of the support cylinder 6.
A main shaft 12 which has the mantle 5 secured thereto through a head center 11 is supported in an upper portion of the eccentric drive shaft 8 rotatably through a radial bearing 13 and in an eccentric and tilted state. A spherical bearing 14 is securely mounted at the upper side of the eccentric drive shaft 8 in sliding contact with a spherical surface 15 formed on the underside of the head center 11.
With this cone crusher, rotation of a drive shaft 16 is transmitted to the eccentric drive shaft 8 through a gear 17 mounted at the fore end of the drive shaft 16 in meshing engagement with a bevel gear 18 on the eccentric drive shaft 8, imparting gyratory rocking motions to the main shaft 12 which is mounted in a tilted state on an upper portion of the eccentric drive shaft 8, by rotation about the axis thereof. Accordingly, the mantle 5 which is mounted coaxially on the mantle shaft 12 through the head center 11 is put in similar gyratory motions eccentrically about the axis of the concave ring 4.
When the mantle is put in such eccentric gyratory motions, rocks which are fed into the clearance between the concave ring 4 and mantle 5, namely, to a crushing chamber 19 is compressed and crushed between the mantle 5 and concave ring 4 by eccentric gyratory motions of the mantle 5. Reaction force F which is produced as a result of compression of the material acts as rotational moment M1 or M2 relative to the main shaft 12 and the eccentric drive shaft 8 which rotatably supports the main shaft 12, and at the same time acts as an axial force pushing the mantle 5 downward. Such rotational moment M1 or the like is set off by the main shaft 12 which is supported in a radial direction by the eccentric drive shaft 8 through the radial bearing 13 and also in an axial direction by the spherical bearing 14, while the axial thrust is absorbed by the spherical bearing 14.
Further, bending moment M1 which is applied to the eccentric drive shaft 8 through the mantle shaft 12 is absorbed by the bearing 7 which supports the eccentric drive shaft 8 in a radial direction, and the axial thrust force is offset by a hydraulic piston 20 which supports a lower portion of the mantle shaft 12.
As is clear from the foregoing description, the rotational moment and thrust force which act on the mantle of the above-described conventional crusher are supported by bearings 7 and 13 in the radial direction in the fashion of a cantilever and by the spherical bearing 14 and hydraulic piston 29 in the axial direction. Accordingly, the bearings are subjected to large reaction forces during the crushing operation and are required to have a sufficiently high load capacity.
Especially, in the conventional crusher of this sort, the main shaft 12 is shrunk-fit on the head center 11 in order to guarantee sufficient strength of the main shaft 12 and the head center 11. However, the head center 11 undergoes deformation on the order of several tens to several hundreds of microns on shrinkage fitting even if the individual units of the head center 11 and main shaft 12 are manufactured with high precision, causing strong localized sliding contact at least either one of the thrust and radial bearings 7, 13 and 14 which are required to absorb thrust or radial loads imposed by the crushing reaction forces through an oil film of several tens of microns in thickness, shortening the lifetime of the bearings.